Populating word list for audio Captcha

I have written a CaptchaService for a web application using Open Source Java. It includes both image and audio. However, I am now faced with populating the word list from which the audio captcha challenge will be randomly selected. Right now it is being done manually.

How have other people done this? My ideas are:

1. Write a WordUtility to grep words from various texts, using specific criteria. Periodically change the text and re-generate the list.
2. Database containing words that can be used for this purpose (I have not yet found an open source one)